Low profile can descender

ABSTRACT

A mining can descender comprising a plurality of strand jacks configured to work in concert to lower a load disposed between a first strand jack and a second strand jack a base configured to accommodate said plurality of strand jacks mounted there to, wherein said base comprises a plurality of assembled sections.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND

1. The Field of the Present Disclosure

This disclosure relates generally to a low profile can descender. Moreparticularly, but not necessarily entirely, this disclosure relates to asystem, method and device for lowering and raising materials with adevice that eliminates the head space limitation inherent in usingoverhead hoist.

2. Description of Related Art

Raising and lowering a load through a vertical space or aperture such asa mine shaft has traditionally been accomplished by the use of a systemthat employs a hoist of one type or another. Illustrations of twoexamples of the prior art are set forth in FIG. 2 and FIG. 3. The hoistsystem commonly comprises a cable and pulley system wherein a cablepasses over a pulley or system of pulleys suspended over the space oraperture. The pulley or system a pulleys is suspended over the verticalspace or aperture via a derrick comprising mutually supporting uprights.A cable passes over the pulley or system of pulleys such that one end ofthe cable is suspended below the pulley and over the vertical space oraperture. The load that is to be raised or lowered is fastened to thisend of the cable. The other end of the cable is wind-ably fastened to aspool. The spool, in turn, is attached to a powering means such that thespool can rotate in both a clockwise or counterclockwise direction. Whenthe spool rotates in one direction, it pays out the cable causing thelength of cable extending below the pulley to lengthen and thus lowerthe load into the hole.

When the spool rotates in the opposite direction, the length of cableextending below the pulley shortens, raising the load from the hole.

A limitation of the traditional pulley and derrick system is the headspace limitation created by the fact that the hoist must be positionedmore or less directly over the hole. The distance between the pulley orpulley system and the top of the hole defines the maximum height of anyobject that may be lowered into the hole at any one time. This isbecause the object must be short enough to fit between the pulley andthe top of the hole.

This height limitation, negatively impacts the usefulness of the pulleyand derrick system when taller items must be lowered into the hole. Anitem that exceeds the head space of the pulley and derrick system mustbe divided into sections that can fit in the head space and loweredindividually into the hole. This method requires a complicated, timeconsuming and potentially dangerous process wherein the first sectionmust be lowered until the top of the section is flush with the top ofthe hole. The first section must be fastened in place by bolts or someother type of a brake mechanism. The cable is then removed from thefirst second while the second section is positioned over the hole, ontop of the first section. The second section is fastened to the firstsection, and the cable is attached, to the second section, the brakingmeans is removed from the first section and the first and second sectionare then lowered into the hole until the top of the second section isflush with the top of the hole. The process is repeated for eachsuccessive section.

The removal of the object is the opposite of the process describedimmediately above. The object is raised until the bottom of theuppermost section is flush with the top of the hole. Then, the object isheld in place by a braking mechanism such as bolts, and the cable isremoved from the uppermost section and the uppermost section isunfastened from the section below and removed from the hole. The cableis then attached to the next section and the process is repeated untilthe entire object is removed from the hole.

The many stops involved with this method of lowering an object into ahole or raising an object from a hole increase the time it wouldotherwise take to lower a tall object into the hole. It also involvesmore labor than would otherwise be required. These factors increase theman hours required and hence increase the cost of performing theoperation. In addition, the braking and un-braking and the fastening andun-fastening of the cables increases the danger and risk of injury tothe persons performing the operation.

In addition, because the traditional pulley and derrick system relies ongravity to position the object of the hole, it is very difficult tocontrol the direction of the object as it is lowered. This makes it verydifficult to use the pulley and derrick system to lower an object into ahole that is net parallel to the normal force, i.e, parallel with theforce of gravity.

Thus, it would be useful if an object could be lowered into a hole allin one piece regardless of the height of the object. It would also beuseful if the angle of the object being lowered could be controlled toaid in lowering an object into a hole that is angled. The problem to besolved to accomplish this goal is to eliminate the head space limitationinherent in the traditional pulley and derrick system. The secondproblem to be solved is to incorporate a directional controllingfunction into the lowering mechanism.

Thus, it is an object of this invention to provide a means to lower andraise an object all a one time. It is also an object of this inventionto provide a means to control the angle of the object as it is loweredfor the purpose of lowering an object into a hole that is angled withrespect to the normal force.

The features and advantages of the present disclosure will be set forthin the description which follows, and in part will be apparent from thedescription, or may be learned by the practice of the present disclosurewithout undue experimentation. The features and advantages of thepresent disclosure may be realized and obtained by means of theinstruments and combinations particularly pointed out in the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the disclosure will become apparent froma consideration of the subsequent detailed description presented inconnection with the accompanying drawings in which:

FIG. 1 is a perspective view of the can descender made in accordancewith the principles of the present disclosure;

FIG. 2 is a perspective view of an operation that illustrates the priorart;

FIG. 3 is a perspective view of an operation that illustrates the priorart;

FIG. 4 is a top view of a base frame;

FIG. 5 is a top view of a base frame;

FIG. 6 is a perspective view of a strand jack;

FIG. 7 is to perspective view of a spacer;

FIG. 8 is a perspective view of a base deck piece;

FIG. 9 is perspective view of a spacer and a jack spacer;

FIG. 10 is a top view of a base frame utilizing strand jack sections;

FIG. 11 is a top view illustrating the frame base with decking partiallyinstalled;

FIG. 12 is a top view of the assembled strand jack system.

FIG. 13 is a top view of the can descender with three strand jacks.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles inaccordance with the disclosure, reference will now be made to theembodiments illustrated in the drawings and specific language will beused to describe the same. It will nevertheless be understood that nolimitation of the scope of the disclosure is thereby intended. Anyalterations and further modifications of the inventive featuresillustrated herein, and any additional applications of the principles ofthe disclosure as illustrated herein, which would normally occur to oneskilled in the relevant art and having possession of this disclosure,are to be considered within the scope of the disclosure claimed.

Before the present to profile can descender is disclosed and described,it is to be understood that this disclosure is not limited to theparticular configurations, process steps, and materials disclosed hereinas such configurations, process steps, and materials may vary somewhat.It is also to be understood that the terminology employed herein is usedfor the purpose of describing particular embodiments only and is notintended to be limiting since the scope of the present disclosure willbe limited only by the appended claims and equivalents thereof.

The publications and other reference materials referred to herein todescribe the background of the disclosure, and to provide additionaldetail regarding its practice, are hereby incorporated by referenceherein in their entireties, with the following exception: In the eventthat any portion of said reference materials is inconsistent with thisapplication, this application supersedes said reference materials. Thereference materials discussed herein are provided solely for theirdisclosure prior to the filing date of the present application. Nothingherein is to be construed as a suggestion or admission that theinventors are not entitled to antedate such disclosure by virtue ofprior disclosure, or to distinguish the present disclosure from thesubject matter disclosed in the reference materials.

It must be noted that, as used in this specification and the appendedclaims, the singular forms “a,” “an,” and “the” include plural referentsunless the context clearly dictates otherwise.

In describing and claiming the present disclosure, the followingterminology will be used in accordance with the definitions set outbelow.

As used herein, the terms “comprising”, “including,” “containing,”“characterized by,” and grammatical equivalents thereof are inclusive oropen-ended terms that do not exclude additional, un-recited elements ormethod steps.

As used herein, the phrase “consisting of” and grammatical equivalentsthereof exclude any element, step, or ingredient not specified in theclaim.

As used herein, the phrase “consisting essentially of” and grammaticalequivalents thereof limit the scope of a claim to the specifiedmaterials or steps and those that do not materially affect the basic andnovel characteristic or characteristics of the claimed disclosure.

As used herein, the term proximal shall refer broadly to the concept ofa nearest portion.

As used herein, the term “distal” shall generally refer to the oppositeof proximal, and thus to the concept of a further portion, or a furthestportion, depending upon the context.

As used herein, the phrase “in an at least partially proximal-to-distaldirection” shall refer generally to a two-dimensional concept ofdirection in which the “proximal-to-distal” direction defines onedirection or dimension. An item that extends in a non-parallel directionwith respect to the “proximal-to-distal” direction, that is, at anon-straight angle thereto, thereby involve two components of direction,one of which is in the “proximal-to-distal” direction and the otherbeing in a direction orthogonal to the “proximal-to-distal” direction.

Turning to FIG. 1, what is shown is an embodiment of the presentinvention depicting an apparatus 100 for raising or lowering a load intoa hole or vertical aperture 126 such as a mine shaft. In this instance,the item depicted is a cylindrical load 102 such as a mine escape way,otherwise referred to as a can. The apparatus 100 depicted in FIG. 1 maybe referred to as a can descender 100. As depicted in FIG. 1, the candescender 100 comprises a plurality of strand jacks 116 configured towork in concert to lower or raise the can 102. Although a strand lack116 is specifically mentioned herein, any comparable device that iscapable of raising or lowering a cable through it via any geared orratchet mechanism known to those of ordinary skill in the art thateliminates the need for a derrick and pulley system may be used.

As depicted here, the strand jacks 116 are affixed to a base frame 120at a point proximal to the base of each strand jack 116. The strandjacks 116 may be removably attached to the base frame 120 or as depictedin FIG. 1, to jack guards 114 attached to the base frame 120. Asdepicted in FIG. 1, the strand jack 116 is attached to the jack guard114 at a point proximal to the base of the stand jack 116. The baseframe 120 is open in the center, with the interior surface of the baseframe 132 defining an aperture 126 through which the can 102 is raisedor lowered. As depicted in FIG. 1, the jack guard 114 is located betweenthe strand jack 116 and the aperture 126. In this position, the jackguard 114 protects the strand jack 116 from being struck by the can 102or other object being lowered into or raised from the aperture 126. Thejack guards 114 also act as guides for the can 102 or other object beingraised from or lowered into the aperture 126.

As depicted in FIG. 1, the base frame 120 comprises a plurality ofcorner sections 110 (depicted in phantom) combined with a plurality ofconnectible sections 112. Although the corner sections depicted herecomprise 90 degree angles, the corner sections may comprise a variety ofangles, such that the base frame 120 may describe a square, rectangle,pentagon, hexagon, or an other polygonal shape. The corner sections 110,may additionally be rounded. The base frame 120 supports a plurality ofdeck sections 136 that overlay the base frame 120. The deck sections 136comprise a radius portion 146 for mechanical communication with the can102 as it is raised or lowered. The base frame 120 is configured toaccommodate a plurality of strand jacks 116 mounted thereon. As depictedin FIG. 1, the strand jacks 116 are angled in such a way that a firstend 130 proximal to the aperture 126 is closer to the load than thesecond end 140 of the strand jack 116, winch end is distal from theaperture 126. The strand jack 116 may then be removably attached to thejack guard 114 via screws, bolts or other means known to those ofordinary skill in the art. The strand jacks may be verticle or possessany other angular orientation with respect to the base frame 120.

The plurality of strand jacks 116 are configured to work in concert toraise and lower a load disposed between them. Each strand jack 116 isoperable independently of the other strand jacks such that the cable 148of one strand jack 116 may be lengthened or shortened to a greaterdegree than the cable 148 of the other strand jacks 116. In this manner,the object being raised or lowered 102 may be tipped and thereforeangled for insertion into or removal from a hole or shaft that isangled.

FIG. 4 depicts an assembled base frame 400 comprised of interlockingsections or spacers 412, first corner sections 414, and second cornersections 410. The base frame 400 is assembleable in either a square orrectangular configuration as follows. The corners are created byconnection the first corner section 414 and second corner section 410.The first corner section 414 is sized and shaped such that its first end416 abuts and removably fastens to the side of the second corner section410 proximal to a first end 418 of the second corner section 410. Thesecond corner section 410 is sized and shaped to connect to the firstend 418 of the first corner section 410. The second end 420 of thesecond corner section 410 and a second end 422 of the first cornersection 414 are sized and shaped to removably connect with a first end424 or second end 426 of the spacers 412. The first end 424 and secondend 426 are also removably attachable to the first end 424 and secondend 426 of other spacers 412. This configuration allows the area of thebase frame 400 can be increased to accommodate any size opening 430 bythe addition of spacers 412.

FIG. 5 depicts another embodiment of a base frame 500. In thisembodiment, the corner sections 510 comprise one piece. The first end514 and the second end 516 of the corner section 510 are sized andshaped to removably attach to the spacers 512. The area of the baseframe 500 can be increased to accommodate any size opening 530 by theaddition of spacers 512 between the corner sections 510. It should beunderstood that the spacers may be of varying lengths in order toaccommodate holes 530 of varying sizes. The lengths may be mixed andmatched to provide a more or less precise fit around any sized hole.

FIG. 6 depicts a side view of a strand jack 616 with the base frame 610depicted in cutaway. The strand jack 616 is angled with respect to thebase frame 610. A jack guard 614 is affixed to a jack guard base 612.The jack guard base 612 is attached to the base frame 610. The lowerportion of the strand jack 616 is attached to a jack guard 614. The jackguard 614 protects the strand jack 616 from being contacted by the canas the can is being either raised or lowered. The jack guard 614comprises a plurality of bumpers 615 to protect the jack guard 614 inthe event it is contacted by the can. The jack guard 614 comprises abase 612 which base is attached to the base frame 610. A first end ofthe strand jack cable 622 extends from the end of the strand jackproximate to the aperture and removably attaches to the can (not shown).In this instance, the strand jack cable end attaches to the base of thecan at a point proximate to the strand jack 616. Additional strand jacks(not shown) attach at other points on the base of the can. As the strandjack cable 622 is payed out through the strand jacks, the strand jackcable extending from the end of the strand jack proximate to theaperture lengthens, causing the can to lower into the shaft. When thecan has been lowered into is appropriate position, it may be secured inplace and the cable ends 630 may be removed.

Each strand jack 616 may be operated independently such that the lengthsof cable 622 extending into the shaft may be varied independently. Thisvarying of the cable lengths allows the can to be angled in any desireddirection allowing the can to be inserted into shafts that are angled.

FIG. 7 depicts a spacer 712. The spacer comprises an end plate 717 withholes 715 for removably attaching the spacer 712 to an adjoining spacer(not shown) or a earner section (not shown) with bolts, screws or anyother fastening means known to those of ordinary skill in the art. Thespacer 712 also comprises a longitudinal surface 724. The longitudinalsurface 724 comprises holes 721 for removably attaching the deck plate.(not shown).

FIG. 8 depicts a deck pane 821 sized and shaped to removably attach tothe upper surface of a base frame (not shown) in order to provide aworking surface over the hole or mine shah as well as to provide forsafety an protection from items or people falling into the hole orshaft. The deck panel 821 has an interior edge 823 that defines a radiussection. The deck panel 821 also comprises a plurality of holes thatcorrespond to holes in the base frame sections (not shown). This allowsthe deck panels 821 to be removably attached to the base frame. The deckpanels 821 may vary in the size and are of their radius section in orderto accommodate different sized base frames and holes or shafts, as wellas different sized cans. In this manner, spacers and deck panels ofappropriate size may be selected to accommodate the diameter of the holethat is being utilized.

In one embodiment, deck panels 821 of the required size and radiussection are selected and removably fastened to the base frame to definea circular interior space whose diameter is slightly larger than thediameter of the can being lowered. This configuration presents theoptimum number of points on the interior surface of the deck panels 821that are in mechanical communication with the exterior surface of thecan to guide the can into position as it is lowered in to the shaft.

FIG. 10 depicts a base frame 1000 with strand jack sections 1014 thatare sized, shaped and configured to be removably attached to the strandjacks (not shown). In this embodiment, the strand jack sections 1014 areflanked by strand jack spacers 1012 b on either side. The strand jackspacers 1012 b are sized and shaped such that the combined length of twostrand jack spacers 1012 b one strand nick section 1014 equals thelength of one spacer 1012 a. In this embodiment, where one or morestrand jack sections 1014 are used, the sides of the base frame with nostrand jack section 1014 can be made equal in length to the sides with astrand jack section 1014 by using one spacer 1012 a.

FIG. 9 is a perspective view of a strand jack spacer 912 b and a spacer912 a. Both the strand jack spacer 912 b and the spacer 912 a comprise alongitudinal section 924 a and 924 b. The longitudinal section compriseholes 920 b, 920 a located on the longitudinal section 924 a and 924 bfor removably attaching the deck sections (not shown). The strand jackspacer 912 b and the spacer 912 a also comprise end pieces 930 a and 930b which end pieces comprise holes 932 a and 932 b for removablyattaching the strand jack spacer and spacer to each other and to otherbase frame members (not shown).

FIG. 11 is a top view of a base frame 1100 with strand jack sections1114 that are sized, shaped and configured to be removably attached tothe strand jacks (not shown). In this embodiment, the strand jacksections 1114 are flanked by strand jack spacers 1112 b on either side,the sides that do not have strand jack sections 1114 or strand jackspacers 1112 b possess spacers 1112 a that are sized and shaped suchthat the combined length of two strand jack spacers 1112 b plus onestrand jack section 1114 equals the length of one spacer 1112 a. ThisFigure illustrates the manner in which the deck sections 1120 are placedover the base frame 1100 and fastened to the base frame 1100 in order toprovide a solid working surface and uniform aperture that correspondsmore or less with the diameter of the hole as well as the diameter ofthe can.

FIG. 12 depicts a top view of a can descender 1210 comprising threestrand jacks 1216. The deck sections 1220 define an interior radius 1230around the shall 1234 through which the can or other load may be raisedor lowered. Strand jack guards 1226 are interposed between the shaft1234 and the strand jacks 1216. This configuration comprises a fourthstrand jack spacer 1224 for the potential attachment of a fourth strandjack 1216. A configuration with three strand jacks 1216 provides anextra point of contact with the can than a two strand jack 1216configuration has. Hence, the three strand jack 1216 configurationprovides a greater degree of control over the can than does a two strandjack configuration 1216. Similarly, a four strand jack 1216configuration provides a greater degree of control over the can thandoes a three strand jack 1216 configuration. However, a three strandjack 1216 configuration provides an opening through which the can may bemaneuvered into place over the hole.

FIG. 3 depicts another embodiment of a can descender 1310 comprising aplurality or strand jacks 1316 on opposite sides of the base frame 1330.The strand jacks 1316 may be paired or may be distributed in pairsaround the opening of the can descender. Pairing the strand jacks wouldallow the can descender to be scaled up to handle heavier loads.

While the above description deals primarily with escape ways, or cans,it should be apparent that the embodiments depicted above may be use forraising or lowering any load into or of a hole. Because the candescender is assembleable from its constituent parts, it can betransported to areas where space is limited, such as underground mines,and assembled where it is needed. This feature, along with the fact thatthe can descender can be used in areas with limited head soiree makesthis device uniquely suited to work underground.

Thus, this can descender is ideally suited for use in mine escape wayinstallation and removal method and system that utilizes, the candescender as depicted in FIG. 1. In this embodiment, the can descender100 comprises a plurality of base frame corner 110 and spacer members112 of differing sizes. The method and system, also comprises asplurality of strand jacks 116 as well as at least one load 111 to beraised or lowered through a mine shaft. The load may be a mine escapeway of the type used to provide a passageway to allow for the egress byminers from one part of the mine to another, especially where thepassageway has a more or less vertical orientation. The can descenderalso comprises a plurality of deck sections 136 of differing sizes.

The method for employing the system comprises selecting the appropriatebase frame members and deck sections required to create a frame and deckstructure with sufficient diameter to match the diameter of the mineescape way being raised or lowered. If the can descender is to be usedbelow the ground, the various selected parts of the system aretransported below ground to the point where the device is to be used. Anescape way of the appropriate size to fit the shaft or aperture intowhich it is to be inserted is also transported to the point where thedevice is to be used. Where space is an issue, the escape way maycomprise connectible sections of sufficient length to fit through thepassageway through which it must pass to get to the point where thedevice is to be used.

Once the appropriate parts are in place, the base frame sections areassembled around the shaft or aperture and the deck sections arefastened in place. The strand sacks are attached to the base frame. Theescape way or escape way segment if placed proximate to the opening ofthe can descender. The cable end of each strand lack is attached to theescape way or escape way segment. Generally, the cable end would beattached proximal to the base of the escape way or escape way segment.The strand jacks are then operated in such a way that the escape way orescape way segment is lowered into the shaft or aperture. In the case ofan escape way that is installed in segments when the first segment islowered to the point where the top of the escape way segment isapproximately even with the deck surface, another escape way segment ismaneuvered into place on top of the first escape way segment andfastened to the first escape way segment. The strand lacks are thenoperated in such a way that the escape way segments are lowered into theshaft or aperture. This process is repeated until all the escape waysegments are installed. The cable ends are then removed, from the escapeway and retracted. The can descender is then disassembled into itscomponent parts and removed from the site.

What is claimed is:
 1. A mining can descender comprising: a plurality ofstrand jacks configured to work in concert to lower a load disposedbetween a first strand jack and a second strand jack; a base configuredto accommodate said plurality of strand jacks mounted there to, whereinsaid base comprises a plurality of assembled sections.
 2. The mining candescender of claims 1, wherein the said base further comprises aplurality of corner sections and a plurality of spacer pieces disposedbetween and connecting said corner sections to form a base frame;wherein said base frame is overlaid with at least one deck section and;wherein said deck sections comprise a radius portion for mechanicalcommunication with said load.
 3. The mining can descender of claim 2,farther comprising a plurality of jack guards corresponding to theplurality of strand jacks and configured to protect said strand jacksfrom contacting said cylindrical load.
 4. The mining can descender of 3,wherein said spacer pieces are configured with attachment structuresdisposed at opposing ends such that a plurality of spacer pieces may beattached in series disposed between said corner portions so as to expandan opening of said base.
 5. The mining can descender of claim 1, whereinthe corner portions comprise: adjoining strait members connected 90degrees to each other to form a corner; and, a decking for connecting tosaid corner, thereby providing a surface that is disposed between saidconnected strait members.
 6. The mining can descender of claim 5,wherein said decking comprises a radius portion.
 7. The mining candescender of claim 6, wherein said radius portion of said decking variesto correspond to the radius of the load.
 8. A mine escape wayinstallation and removal system comprising: at least one escape waysegment for placing within a mine shaft; a plurality of strand jacksconfigured to work in concert to lower an escape way segment disposedbetween a first strand jack and a second strand jack; a base configuredto accommodate said plurality of strand jacks mounted there to, whereinsaid base comprises a plurality of corner sections; wherein said cornerportions comprise a curved portion for mechanical communication withsaid escape way segment; and a plurality of jack guards corresponding tothe plurality of strand jacks and configured to protect said strandjacks from contacting said escape way segment;
 9. The system of claim 8,wherein said spacer pieces are configured to be used in series disposedbetween said corner portions so as to expand an opening of said base.10. The system of claim 9, wherein the spacer pieces are configure withattachment structures disposed at opposing ends such that a plurality ofspacer pieces may be attached in series.
 11. The system of claim 10,wherein the corner portions comprise: adjoining strait members connectedat an angle relative to each other to form a corner and, a decking forconnecting to said corner thereby providing a surface that is disposedbetween said connected strait members.
 12. The system of claim 11,wherein said decking comprises a radius portion.
 13. The system of claim12, wherein said radius portion of said decking is variable tocorrespond to the radius of the escape way.
 14. The system of claim 10,farther comprising spacer pieces that are sized to accommodate theplacement of said strand jacks within said frame.
 15. The system ofclaim 10, wherein said can descender comprises two strand jacks and twocorresponding jack guards.
 16. The system of claim 10, wherein said candescender comprises three strand jacks and three corresponding jackguards.
 17. A mining escape way installation method comprising:assembling a base frame by attaching at a plurality of corner sectionsand spacer pieces; attaching a plurality of strand jacks to said baseframe; attaching at least one deck section to said base frame; whereinsaid deck section comprises a radius portion; placing an escape waysegment within an opening of a can descender; connecting a first cableof a first strand jack to said first escape way segment; connecting asecond cable of a second strand jack to said first escape way segment;and, operating said first strand jack and said second strand jack so asto lower said escape way segment into a mine opening;
 18. The method ofclaim 17, further comprising attaching spacers between said cornerportions so as to expand said opening to accommodate larger diameterescape ways.
 19. The method of claim 18, wherein said spacers areconfigured with attachment structures disposed at opposing ends suchthat a plurality of spacers may be used in series disposed between saidcorner portions so as to expand an opening of said base.
 20. The methodof claim 17, wherein the corner portions comprise adjoining straitmembers connected at an angle relative to each other to form a corner.21. The method of claim 17, wherein said radius portion of said decksection varies corresponding to the diameter of the escape way.
 22. Thesystem of claim 19 further comprising spacers that are sized toaccommodate the placement of said strand jacks within said frame. 23.The system of claim 19 wherein said can descender comprises two strandjacks and two corresponding jack guards.
 24. The system of claim 19wherein said can descender comprises three strand jacks and threecorresponding jack guards.
 25. The mining can descender of claim 1,wherein the plurality of strand jacks are paired on said base frame toincrease load capacity.